Enamel glaze composition

ABSTRACT

An enamel glaze composition containing the first component comprising an inorganic carbonaceous material or one or more selected from the group consisting of Al, Si, Ti, V, Cr, Mn and Fe and the second component consisting of a high valency oxide of poly-valent metal or a double oxide thereof with an oxide of alkali or alkaline-earth metal to provide an excellent enamel having no defect of fishscale on a steel sheet.

United States Patent Kitayama et al.

[ Dec. 23, 1975 Appl. No.: 314,665

Foreign Application Priority Data July 18, 1972 Japan 47-71230 July 20, 1972 Japan 47-71989 US. Cl. 106/48 Int. Cl. C03C 5/02 Field of Search 106/48, 48 C; 117/129 References Cited UNITED STATES PATENTS 6/1947 Amberg 106/48 Rex 106/48 2,658,834 11/1953 2,786,782 3/1957 Zimmerman et a]. 106/48 3,169,217 2/1965 Dalton 106/48 3,338,694 8/1967 Davy 106/47 R Primary ExaminerWinston A. Douglas Assistant Examiner-Mark Bell Attorney, Agent, or FirmToren, McGeady and Stanger [57] ABSTRACT An enamel glaze composition containing the first component comprising an inorganic carbonaceous material or one or more selected from the group consisting of Al, Si, Ti, V, Cr, Mn and Fe and the second component consisting of a high valency oxide of poly-valent metal or a double oxide thereof with an oxide of alkali or alkaline-earth metal to provide an excellent enamel having no defect of fishscale on a steel sheet.

3 Claims, 16 Drawing Figures US. Patent Dec. 23, 1975 SheetlofS 3,928,048

FIG.1

Various properties of the 10 glaze are deteriorated.

. Foam Fishscale l5 Sco of P esent and Addition of high valency 1 not prevented' I S r unevennies oxideof pol -valent 0 Ion occur metal. parts per 100 parts of frit.

0.1- Fishscale is not prevented Addition of inorganic carbonaceous material. parts per100 parts of frit.

Various properties of the 0 glaze are deteriorated.

P h c g Foam and 1 -prevented, I unevenness occur The second component. parts per 100 parts of trit.

Al as the first component. parts per 100 parts of trit.

US. Patent Dec.23, 1975 Sheet20f5 3,928,048

(1) glaze layer U.S. Patent Dec. 23, 1975 Sheet30f5 3,928,048

FIG.4,2

FIG

FIG

FIG-.43

U.S. Patent Dec. 23, 1975 Sheet40f5 3,928,048

FIG.5,I FIG.5,2

F|G.7,l FIG-7,2

U S. Patent Dec. 23, 1975 Sheet 5 of 5 3,928,048

FIG.6,2

FIG. 6,l

FIGS,

FIG

ENAMEL GLAZE COMPOSITION The present invention relates to an enamel glaze composition, particularly to Offer an enamel glaze composition which provides an excellent enamel coating having no fishscale on a steel sheet.

According to the grade of steel sheet, the formation of fishscale has been unavoidable on the surface of the enamel applied thereon in using a conventional enamel glaze composition in some instances according to the the burning condition used. Steel sheets for enameling are usually cold rolled steel sheets of a rimmed or capped steel. The use of cold rolled steel sheet of aluminium killed steel as well as hot rolled steel sheet has been restricted only for special purposes which are satisfied by one side enameling, because fishscale is formed when both sides are enameled.

The defect of fishscale means a phenomenon in which the surface layer of a burnt enamel film is broken to shell-like fine pieces after burning. The reason of the formation of fishscale is considered as follows:

A trace amount of moisture coming from the glaze remains unavoidably in the enamel during burning and reacts with steel as a base metal to form hydrogen as in the equation,

Fc (base steel sheet) H2O FcO 2H (to the interior of steel sheet).

The hydrogen thus produced is occluded in the steel sheet, and escapes out of the steel sheet as a high pressure gas when the solubility of hydrogen in steel is decreased in the stage of cooling after burning, and the stress due to said high pressure gas breaks the surface layer of the solidified enamel film to form fishscale.

In accordance with this mechanism of the occurence of fishscale, the following means have been considered for preventing the defect of fishscale:

1. To remove the influence of moisture in the glaze,

2. to increase the solubility and diffusion resistance of hydrogen in the steel sheet after cooling, and

3. to release the stress due to hydrogen escaping from the steel sheet.

The means noted in (2) must be applied to the steel sheet itself. Thus, the steel grade as well as the history of hot and cold rolling produce various solubility properties to the steel.

Aiming at the means noted in (1) and (3), the present invention has succeeded after various investigations on the use of various additives to the glaze.

The enamel glaze composition of this invention comprises 100 parts of enamel frit, 0.003 0.3 part as C of an inorganic carbonaceous material, 0.1 10 parts of a high valency oxide of poly-valent metal, such as, C 0 and BaO and other mill additives commonly used for the glaze. (The amount is expressed in weight. The same is also applied hereinafter.)

Another enamel glaze composition of this invention comprises 100 parts of enamel frit, 0.003 0.3 part as C of inorganic carbonaceous material, 0.05 parts of a double oxide between a high valency oxide of pOly-valent metal and an oxide of alkali or alkalineearth metal and other mill additives commonly used for the glaze.

The present inventors have studied further to substitute said inorganic carbonaceous materials with some kinds of metal, obtaining a very favourous result.

Thus, a further enamel glaze composition of this invention comprises 100 parts of enamel frit, 0.03 3

part of the first component containing one or more selected from the group consisting of Al, Si, Ti, V, Cr,

Mn and Fe as a main constituent, 0.05 10 parts of the second component consisting of a high valency oxide of poly-valent metal or 0.01 10 parts of a double Oxide thereof with an oxide of alkali or alkaline-earth metal and other additives commonly used for the glaze.

The details of the invention will be set forth in the following.

FIG. 1 is a graph showing the effect of the addition amounts of an inorganic carbonaceous material and a high valency oxide of poly-valent metal.

FIG. 2 is a graph showing the relation between the addition amounts of Al and a high valency oxide of polyvalent metal and various properties of the enamel including such defects as fishscale, blister and unevenness.

FIG. 3 is to illustrate the difference in the behavior of moisture between the conventional and the present cases.

FIGS. 4, 5, 6 and 7 are the photographs of the appearance of burnt enamel in Examples 1, 2, 5 and 6.

FIG. 1 shows the relation between the amounts of the 'two additives and various properties of the enamel obtained including such defects as fishscale, blister and unevenness in the case when a cold rolled, aluminium killed steel sheet is coated on both sides with a glaze composition containing an inorganic carbonaceous material and Ni O as a ground coat, burnt for 3 minutes at 850C, and a cover coat enamel is applied thereon.

As obvious from the figure, the formation of fishscale cannot be prevented when the inorganic carbonaceous material is less than 0.003 parts as C per parts of enamel frit, and also when the high valency oxide is less than 0.1 part. On the other hand, when the inorganic carbonaceous material exceeds 0.3 part as C, such defects as blister and unevenness occur on the enamel film after burning. When the high valency oxide of poly-valent metal exceeds 10 parts, various undesirous results of the glaze occur, such as, the increases in the viscosity of slip and the expansion coefficient of the glaze after burning.

It is concluded, therefore, that, in order to prevent the formation of fishscale without the accompanying defects, the composition comprising 100 parts of enamel frit, 0.003 0.3 part as C of an inorganic carbonaceous material and 0.1 10 parts of a high valency oxide of poly-valent metal is most suitable.

Inorganic carbonaceous material used in this invention are, for example, graphite, active carbon, wood charcoal and metal carbide. A mixture of them may naturally be applied.

High valency oxides of poly-valent metal applicable are, for example, BaO C0 0 Ni O MnO SnO and Sb O A mixture of these may also be applied. Low valency oxides such as BaO, C00,.Mn0 and SnO have no effect.

However, as high valency oxides of poly-valent metal are generally insoluble in water, they disperse in the glaze with difficulty, making the slip of glaze composition non-uniform, and the high valency oxide contacts with the carbonaceous material with difiiculty.

Accordingly, the present inventors have made further investigations and found that, by leading a high valency oxide of poly-valent metal to a double oxide with an oxide of alkali or alkaline-earth metal,

1. such a double oxide becomes soluble in water, or even when it is insoluble in water, it disperses easily in the aqueous slurry (slip); and consequently,

2. various defects due to the non-uniform dispersion of the glaze at high temperature such as the formation of blister and unevenness on the enamel surface can completely be prevented.

Since not only the double oxide disperses easily in the slip, but also its density becomes lower, no sedimentation takes place, and consequently, the workability becomes excellent.

The use of double oxide exhibits its effect particularly in a one coat enamel to which a severe surface finish is desired.

The formation of fishscale cannot be prevented when the double oxide is less than 0.05 part. When the double oxide exceeds 10 parts, various undesirous results occur as in the former case. The range of the addition amount of carbonaceous material is also as before.

Double oxides between a high valency oxide of polyvalent metal and an oxide of alkali and alkaline-earth metal which can be used are, for example, Na O.- SnO .3I-I O, CaO.SnO .3H O, K O.Sb O .7H O, Na O.Bi O nCaO.mMnO K O.CaO.3CoO KMnO and K Cr O A mixture of these may also be used. Low valency double oxides have no effect.

Now, the effect of using the first component such as aluminium will be set forth.

FIG. 2 shows the relation between the addition amounts of aluminium as the first component and SnO or Na O.SnO as the second component and various properties of the enamel obtained. The experimental conditions were the same as in FIG. 1.

The formation of fishscale cannot be prevented when the aluminium as the first component is less than 0.03 part as effective AL, and also when SnO as the second component is less than 0.05 part (as line (I) in the figure) or when Na O.SnO as the second component is less than 0.01 (as line (2)). On the other hand, when aluminium exceeds 3 parts as effective Al, such defects as blister and unevenness occur on the enamel surface after burning. When SnO or Na O.SnO as the second component exceeds 10 parts, various undesirous results of the glaze occur such as the increases in the viscosity before burning and the expansion coefficient after burning.

Thus, it is concluded that, in order to prevent the formation of fishscale without accompanying said defects, the composition comprising 100 parts of enamel frit, 0.03 3 parts as effective amount of the first component and 0.05 10 parts of a high valency oxide of poly-valent metal, or 0.01 10 parts of a double oxide between a high valency oxide of poly-valent metal and an oxide of alkali or alkaline-earth metal of the second component is most suitable.

The first components used in this instance are, for example, Al, Si, Ti, V, Cr, Mn and Fe. A mixture of these may naturally be applied. Other metals are not suitable, because their reactivity is too great or too small, or they are too costly.

High valency oxides of poly-valent metal and their double oxides with oxides of alkali or alkaline-earth metal which are suitable are the same as in the above instances.

Although the reason why the enamel glaze compositions in the present invention exhibit said remarkable effect is not yet certain, it may be considered as follows: I

4 In the conventional method, moisture coming from the glaze reacts with iron at the surface of the base metal during burning to form hydrogen, and the hydrogen thus produced is occluded in the base metal as in equation (1) (cf., FIG. 3(a)),

1. Fe H O FeO 2H (occluded in the steel).

FeO produced serves, on the other hand, to adhere the glaze firmly to the base metal.

As compared with this, in adding an inorganic carbonaceous material together with a high valency oxide of poly-valent metal, in the form of simple as well as double oxides, in this invention, the mechanism may be as shown in the following equations (cf., FIG. 3(b)):

1'. 6(Fe H O) 0(Fe +2H (occluded in the steel) 3. (l 0) (C +H O) (1 0) (C0 H (escapes out of the system)), and

4. (1 6) (Fe+O) (l 0) FeO.

The essential merit of adding an inorganic carbonaceous material is that a part of the moisture is decomposed with carbon to produce gaseous hydrogen according to equation (3), which escapes out of the system without remaining in the steel as the reaction takes place in the glaze layer; and consequently, in the presence of carbon, the hydrogen occluded in the steel is reduced to 0 times 0 1) as in (1), thus preventing the formation of fishscale.

The excess of carbon is decomposed by the reaction (2). Oxygen used for the reactions (2) is supplied by the spontaneous decomposition of the high valency oxide of polyvalent metal or the reduction thereof with carbon added at the same time. The remainder of oxygen thus produced is used for the reaction (4).

The reaction in total, (1 2 3 4), becomes cluded) (1 0) H escapes), and accordingly, the amount of iron oxidized to FeO at the surface of the base metal is the same as in (1).

As a result, the formation of fishscale is prevented sufficiently, and the adhesion of the glaze to the base metal is not deleteriously affected at all. Moreover, due to the escape of CO gas formed by the reaction (2) and CO gas produced therefrom from the glaze during burning, the enamel possesses a fine bubble structure, and the bubble structure may serve to release the hydrogen pressure which causes the formation of fishscale and to make the surface of the enamel smooth and foamless. Too much carbon makes the bubble structure of the enamel inferior.

The mechanism in using the first component such as aluminium may be considered similarly. For instance, aluminium reacts as follows:

(2) 2A1 +30 A1 0 and (3') 2A1 3H O A1 0 3H (escapes out of the system).

As no gas is evolved in using aluminium and others, a larger amount can be added as compared with the case of an inorganic carbonaceous material. Too much amount thereof causes, as already mentioned, many problems in the glaze such as an increase in the viscoslty.

In the course of the present investigation, the present inventors tried to add merely an inorganic carbonaceous material. A' passable effect was obtained, but was unsatisfactory.

effect is observed insofar as preventing the formation of fishscale. Moreover, as hydrogen is produced from organic materials, a reverse effect with respect to preventing the formation of fishscale is observed.

In manufacturing the enamel slip in this invention,

silica powder, clay, setting agent (inorganic salts to control the viscosity of the slip) etc. may be added as usual as mill additives to the enamel frit, andthe mixture is milled. Considering the trends in the properties of the slip, the dried slip film after coating and the burnt enamel film, the use of setting agent may be omitted or the brightening agent (such as urea) may be added. 7

EXAMPLE 1 001 part as C of graphite powder and 1 part of C 0 were added to 100 parts (as solid matter) of Slip H made of Japan Ferro Co. The mixture was applied by immersion on a 0.8 mm aluminium killed, cold rolled steel sheet to which the usual pre-treatment for enameling was effected, and burnt for 3 minutes at 850C (Sample A). A titanium white cover coat enamel was applied on Sample A (Sample AX).

For comparision, Slip H as it stands was applied on the same steel sheet, and burnt similarly (Sample B); and the same cover coat enamel as above was applied on Sample B (Sample BX).

The results were as follows; and their photographs were as shown in FIG. 4.

A No surface defects such as fishscale (even after l month) (FIG. 4, l).

AX do. (FIG. 4, 2)

B Fishscale was formed on all over the surface after one day and night (FIG. 4, 3).

BX Damaged due to splitting of the slip during burning (FIG. 4, 4).

EXAMPLE 2 Basic composition:

Frit XG 141 made of Japan Ferro Co. parts Frit XG I42 made of Japan Ferro Co. 30 parts Frit XG 145 made of Japan Ferro Co. parts Silica powder l0 parts Clay 7 parts Inventive slip:

0.03 part as C of active carbon and 2 parts of BaO were added to said basic composition containing 100 parts (as solid matter) of the slip, and the mixture was milled (Sample C).

Slip for comparison:

A settling agent (0.75 part in total comprising borate, sodium nitrite and magnesium carbonate) was added to said basic composition, and the mixture was milled (Sample D).

Both slips were applied by spraying on both sides of a 2.3 mm hot rolled steel sheet previously shot-blasted, and was burnt for 4,5 minutes at 850C.

Results:

6 C No surface defects such as fishscale (even after 1 month) (FIG. 5, 1). D Fishscale was formed on-all over the surface after one'day andnight (=FIG. 5, 2).-

EXAMPLE 3;

In Examples 3 and .4, the use of a double oxide will be illustrated. I

Conventional slip (Sample C):

A frit made of Japan Ferro Co. lOO parts (titanium white opaque frit) Clay p v 7 parts Magnesium carbonate 0.25 parts Sodium nitrite 0.25 parts Water 45 parts Particle size 2 3 g/200 mesh/5O ml slip Inventive slips:

Sample A 0.03 part of carbon and 1 part of K 0.- SnO .3H O were added to 150 parts of said conventional slip. I

Sample B--. 0.03 part of carbon and 1 part of BaO were added to 150 parts of said conventional slip.

These three slips were, respectively, applied by spraying on both sides of a 1 mm decarburizedaluminium killed cold rolled steel sheet previously acid pickled and nickel plated as usual, and were burnt for 2 minutes at 840C.

Results:

A No surface defects such as fishscale.

B No formation of fishscale, but one unevenness with a diameter of 0.05 mm was found per dm of the surface.

C Fishscale was formed on all over the surface after one day and night.

EXAMPLE 4 Basic composition:

Frit made of Japan Ferro Co. 2232 35 parts Frit made of Japan Ferro Co. 2236 35 parts Frit made of Japan Ferro Co. 2240 30 parts Silica powder 5 parts Clay 7 parts Inventive slip (Sample A):

0.1 part of carbon and 0.5 part of Na O.SnO .3H O were added to basic composition containing parts of the frit, and the mixture was milled.

Slip for comparison (Sample B):

A setting agent was added to said basic composition, and the mixture was milled.

Said conventional slip B was applied by spraying on both sides of a 2.3 mm hot rolled, rimmed steel sheet previously shot-blasted and was burnt (B l).

Inventive slip A was applied and burnt on the same steel sheet similarly (A 1).

Said slip B was applied and burnt on an enameled product having numerous fishscale defects (B 2).

Inventive slip A was applied and burnt on an enameled product having numerous fishscale (A 2).

Results:

A-l No surface defects such as fishscale and unevenness.

A-2 No surface defects such as fishscale and unevenness.

B-l Fishscale was formed.

B-2 Fishscale was formed.

EXAMPLE "5;,

Examples 5 and 6 are to show the effect of silicon and aluminium as the representatives of the first component.

0.3 part of silicon and 0.3 part of MnO were added to I parts (as solid matter) of Slip H made by Japan Ferro Co., the mixture was applied by immersion, on both sides of a continuous cast aluminium killed hot strip sheet, and burnt for 4 minutes at 860C (Sample C). A titanium white cover coat enamel was applied on Sample C (Sample CU).

For comparison, said Slip H as it standswas applied similarly on the same steel sheet (Sample D). Said titanium white cover coat enamel was applied on Sample D (Sample DU).

Results:

C No formation of fishscale even after 1 month (FIG. 6, l).

CU do. (FIG. 6, 2).

D Fishscale was formed after 24 hours (FIG. 6, 3).

DU Large amount fishscale (FIG. 6, 4).

EXAMPLE 6:

Basic composition:

Frit 2232 made of Japan Ferro Co. 35 parts Frit 2236 made of Japan Ferro Co. 35 parts Frit 2240 made of Japan Ferro Co. 30 parts Silica powder parts Clay 7 parts Inventive slip:

0.5 part of aluminium and 1 part of Na O.SnO .3H O were added to said composition containing I00 parts of the frit, and the mixture was milled (Sample A).

Conventional slip: l

A settling agent (0.75 part in total comprising borax and sodium nitrite), was added to said basic composition, and the mixture was milled (Sample B).

Both slips were applied by spraying on both sides of a 2.3 7 mm hot rolled, rimmed steel previously shot-blasted, and were burnt for 4.5 minutes at 860C.

Results:

A No fishscale and other surface defects even after 1 month (FIG. 7, l). B Fishscale was formed on all over the surface after 24 hours (FIG.'- 7, 2).

What'is claimed is:

I. In an enamel glaze composition for coating onto steel sheets of the type composed of an enamel frit and conventional 'mill additives, the improvement consisting essentially of said composition further containing from 0.03 0.3 parts by weight as carbon of an inorganic carbonaceous material and 0.1 10 parts by weight of a high valency oxide of a poly-valent metal, per parts by weight of said enamel frit to prevent the formation of fishscale.

2. An enamel glaze composition as set forth in claim 1 in which the inorganic carbonaceous material comprises graphite, active carbon, wood charcoal or metal carbide, or a mixture of them.

3. An enamel glaze composition as set forth in claim 1 in which the high valency oxide of poly-valent metal comprises BaO C0 0 M 0 MnO SnO or Sb O or a mixture of them. 

1. IN AN ENAMEL GLAZE COMPOSITION FOR COATING ONTO STEEL SHEETS OF THE TYPE COMPOSED OF AN ENAMEL FRIT AND CONVENTIONAL MILL ADDITIVES, THE IMPROVEMENT CONSISTING ESSENTIALLY OF SAID COMPOSITION FURTHER CONTAINING FROM 0.03 - 0.3 PARTS BY WEIGHT AS CARBON OF AN INORGANIC CARBONACEOUS MATERIAL AND 0.1 - 10 PARTS BY WEIGHT OF A HIGH VALENCY OXIDE OF A POLYVALENT METAL, PER 100 PARTS BY WEIGHT OF SAID ENAMEL FRIT TO PREVENT THE FORMATION OF FISHSCALE.
 2. An enamel glaze composition as set forth in claim 1 in which the inorganic carbonaceous material comprises graphite, active carbon, wood charcoal or metal carbide, or a mixture of them.
 3. An enamel glaze composition as set forth in claim 1 in which the high valency oxide of poly-valent metal comprises BaO2, Co2O3, Ni2O3, MnO2, SnO2 or Sb2O5, or a mixture of them. 